1. Field of the Invention
The present invention relates to a device and a method of driving a stepping motor of an analog electronic clock.
2. Description of the Related Art
A stepping motor driving apparatus of an analog electronic clock includes a stepping motor and a driving section that drives the stepping motor. The stepping motor includes a rotor, a stator, and a coil. The driving section includes a detection circuit that detects whether or not the rotor is rotated immediately after the stepping motor is driven by a regular pulse having a certain pulse width. At this time, when the detection circuit detects non-rotation of the rotor, a correction pulse, by which the rotor may be rotated under a worst condition, is output immediately, and then switching is made to a wider pulse that is one level wider than the regular pulse to driving the rotor. When the detection circuit can detect rotations continuously for a predetermined number of times or a predetermined period (for example, 60 times or 60 seconds) (non-rotation is not detected), switching is made to a pulse that is one level narrower to driving the rotor.
As described above, by controlling to driving the rotor by a pulse that is narrower as much as possible, power consumption of a battery is restricted to the utmost.
However, in the stepping motor driving apparatus described above, when another high load element than the stepping motor is driven by the battery, a phenomenon where a voltage of the battery is lowered temporarily for a short period is occurred. When the rotor is not rotated due to the temporary lowering of the voltage for a short period, the correction pulse is output, and then the wider pulses are continuously output for a predetermined number of times or a predetermined period (for example, 60 times or 60 seconds), as described above.
For this reason, even if the lowering of a voltage is temporary for a short period and recovery of the voltage is made immediately, wider pulses that require higher power consumption than that of the regular pulse are continuously output for a predetermined number of times or a predetermined period, and wasteful power consumption is generated.